This invention relates in general to the structural support for light weight panels. More specifically it relates to structural elements which comprise preforms of any moldable, deformable or laminar material like paper, cardboard, plastics, reinforced resins, metals, alloys, compound materials, agglomerates, asbestos, gypsum, ceramic, glass or any other similar material, any of which is formed in such a way as to have a very high structural resistance to compression and to flexure, maintaining a low weight and having a configuration which allows to comprise support points to which other preforms or sheets of any material can be affixed to construct the structural elements.
The technical aspects and advantages of structural sandwich panels are well known, because they have been used for structures that require a very high resistance and a very low structural weight. The so called honeycomb sandwich panels are well known among this type of panels. In this type of structures, the panel is constructed by means of strips of the material used that are fixed together at some points in such a way that the hexagonal honeycomb is established, in which such honeycombs extend perpendicularly to the sheet or sheets with which the sandwich is constructed. The strips that form the honeycomb extend longitudinally in a cross sectional way to the sheet or sheets that form the sandwich. This means that the strips forming the honeycomb extend perpendicularly to the sheets that form the sandwich panel. Other configurations different to hexagonal can be used like triangular, pentagonal, etc.
Different materials can also be used for the construction of sandwich panels, both for the core as well as for the sheets that form the walls of the sandwich. Such materials can be for example, paper, cardboard, plastic, metal and composite materials. The basis of the sandwich panels rest in keeping a core that work as a perpendicular structure support for the panel, while other configurations adopted throughout the time, allow to distribute the effort applied all over the panel in a more or less homogenous manner, which allow to decrease up to ten times the weight of the structural element in comparison with traditional structural elements formerly used, keeping under the same conditions the under load support capacity. This type of structures have had huge advantages by supporting the same loads at a fraction of the weight and cost of prior structural elements.
Different methods to build sandwich panels by diverse techniques have been discussed. A notable example could be found in U.S. Pat. No. 5,028,474 dated Jul. 2, 1991, granted to Ronald M. Czaplicki entitled Cellular Core Structure providing Gridlike Bearing Surfaces on Opposing Parallel Planes of the Formed Core.
Among the inventions made to give structural cores to sandwich panels is U.S. Pat. No. 3,865,679 dated Feb. 11, 1975, granted to Jesse R. Hale, entitled Sandwich Panel having Cellular Core Structure with Reinforcing Elements, which teaches a core structure that has nodes, shown in essentially circular manner, that project in opposed directions form a mid plane with apices of said nodes abutted against the face sheets of the panel, comprising first reinforcing bar means running along to the sides of a first row of said nodes, wherein said bar means are bonded to the sides of said nodes of said center and to the surface of one of the face sheets of the panel and a second reinforcing bar means that run along of a second row of said nodes, wherein said second reinforcing bar means are bonded to the surface of one of the face sheets. This patent comprises as improvement the addition of reinforcing bars that are bonded to the face sheets of the nodes along two different rows of nodes and are bonded by the ends to the face sheets of the sandwich panel. It is evident that the structure used in this invention, requires an additional reinforcement to support the stress that will be applied to the panel and will not be discussed in more detail.
In U.S. Pat. No. 5,028,474 above described, in a three dimensional structure that comprises ridges and essentially lineal valleys which establish spaced rows of adjacent inclined rectangular shaped facets connected by intermediate rows of adjoining parallelogram-shaped facets, wherein said structure is made by folding of a continuous unbroken sheet material, wherein said laminate material has a superficial area and said superficial area is filled of a repetitive path of cellular units. The central structure provides support surfaces of the grid type in two support plan parallel opposed to which the plates or sheets can be fixed as faces to form the panel in the form of a sandwich.
From the prior description and the accompanying drawings to the patent of Czaplicki, it should be appreciated the problem to establish the actual way in which the plate or sheet is folded, which finally constitutes a three dimensional figure but with different geometric figures. This relative obstacle to fold the plate or sheet does not allow to adequately appreciate the value of this invention. U.S. Pat. No. 5,182,158 dated Jan. 26, 1993, granted to Barnarr C. Shaeffer titled Lightweight Sandwich Panel, wherein in a sandwich panel which comprises external layers which has projections bonded to the other external layer, wherein the projections have relatively flat areas in their edges, in the edges freed to provide enlarged areas for bonding, wherein the flat areas are bonded chemically to the other external layer, the core layer is a plastic sheet and the projections are formed from the sheet and the projections by area would vary in density to provide different resistances to the deflection in various parts of the panel, wherein one of the external layers is transparent and the core layer is dark to absorb the sun's ray and is open to the passage of air through it. It can be clearly appreciated from the prior description that the patent to Schaeffer has been designed for its application to aviation in general, wherein it can be appreciated in FIGS. 2 to 4 that different cross section sheets are used also bonded to form a honeycomb. In FIG. 5 it could be appreciated a structure with steep projections. The instant invention differs from Shaeffer as will be herein further described. From the foregoing it could be appreciated that these structures in the form of sandwich are formed by three or more pieces, which makes very complex its construction, structure or use. Diverse geometrical shape panels with thin metallic sheets have also widely been described, like in U.S. Pat. Nos. 3,209507; 3,622,430; 3,834,487 and 3,938,963, or there are also inclusive those patents which illustrate systems of the multiconical type as U.S. Pat. Nos. 4,672,780 and 4,794,742, but in none of these cases, these patents have the advantages of the instant invention.